Drusen are deposits that form under the retina. They look like yellow spots in the retina and their presence is often a precursor to more serious macular degeneration. The retina is located in the back of the eye and functions like film in a camera. The retinal photoreceptors (rods and cones) are metabolically active and require a rich blood supply to function properly. Drusen are accumulations of “debris” that form under the retina, blocking the transfer of nutrients and oxygen between the retina and the supporting choroid (a bed of blood vessels that nourish the retina) underneath. This blockage of nutrition transport causes the retina to slowly atrophy and can lead to significant visual dysfunction over time. This process is called macular degeneration. “Macular drusen” should not be confused with optic nerve drusen which are calcium crystals in the optic disk that rarely cause visual problems.